.navigator_proveedores{
    background-image: url(http://www.mundo.com/assets/images/proveedores.png);
}
.button_add{
    background-image: url(http://www.mundo.com/assets/images/add.png);
}
.button_sync{
    background-image: url(http://www.mundo.com/assets/images/arrow_refresh.png);
}